1. Field of the Invention
The present invention relates to lens modules and more particularly, to an anti-EMI (static electricity, radiowave and electromagnetic interference) lens module for use in a bill acceptor for detecting the authenticity of a bill. The lens module has multiple positioning structures to have a lens device positively and accurately positioned in between a holder base and a top cover.
2. Description of the Related Art
Following fast development of technology, our mode of living has been changed. Various automatic vending machines (card dispensers, ticket vending machines, money exchanging machines, etc.) are used everywhere to sell any of a variety of products without serviceman. Providing automatic vending machines saves much labor cost, and brings great convenience to consumers. A money-exchanging machine generally comprises a coin acceptor and a bill acceptor.
However, venders and consumers are always assailed by the problem of counterfeit money since the use of paper currency. Following development of computer technology, evil persons may use a computer to scan, copy and print paper money. Therefore, a paper currency has anti-counterfeiting techniques. Visible anti-counterfeiting techniques of paper currency include paper material, ink, seal, mark and etc. that can easily be verified with the eyes. However, examining invisible anti-counterfeiting techniques requires a precision bill acceptor or validator. A bill acceptor or validator for this purpose uses electric recognition devices to detect different characteristics of bills or valuable securities.
However, the use of a bill acceptor or validator must consider the problem of interference of internal electromagnetic noises from internal electronic devices and external electromagnetic noises from external cell phones or radio transmitting devices. Under the interference of static electricity, radiowave or electromagnetic noises, the electric recognition devices (such as photo sensors) may produce a false signal, lowering the reliability of the bill acceptor or validator.
Further, either conductors or non-conductors may produce electric charges under a certain condition. Almost all substances can produce static electricity. When a valuable security (banknote, license, IC card) is inserted into an automatic vending machine, the plastic (or rubber) rollers of the bill transferring mechanism are rotated to carry the inserted security forwards for recognition. Friction between the plastic (or rubber) rollers of high insulative resistance of the bill transferring mechanism and the valuable security may produce static electricity of static potential as high as 10 KV. The amount of cumulative static electricity has a great concern with the speed of the rollers of the bill transferring mechanism. The faster the speed of the rollers is, the higher the cumulative amount of static electricity will be. Therefore, the conventional bill acceptor or validator has the following drawbacks:
1. After a long use of the machine, a big amount of static electricity will be cumulated in the plastic shells, and cumulated static electricity will be discharged from the plastic shells when reached a certain amount. This discharge of static electricity will interfere with the functioning of the IC chips of the recognition devices of the bill acceptor or validator, causing a recognition error. Further, external electromagnetic noises may also interfere with the performance of the bill acceptor or validator, resulting in a recognition error. Therefore, conventional bill acceptor or validator may frequently receive a big amount of false bills. Further, a recognition error may cause machine shutdown.
2. When an automatic vending machine is used to sell tobacco, alcohol, drugs or other controlled products, it needs to recognize the age or real identification of the client and stores the related data in the memory of the bill acceptor for checking whether the client meets the legal age requirement or not. A static electricity interference may cause loss of storage data, resulting in unrecoverable consequences.
3. When electric charges are discharged after accumulation of a big amount of static electricity, an electric shock may occur in the internal electronic devices or circuit board of the bill acceptor or validator, causing damage to the electronic devices and memory of the machine. This damage may result in a big loss or increase of maintenance cost.
4. Discharge of static electricity may damage the bill acceptor, and discharging sparks may cause inflammable gas or substance (valuable securities) to burn. Burning of inflammable gas or substance in the bill acceptor may cause the automatic vending machine to explode, resulting in an unexpected catastrophe.
Therefore, it is desirable to provide a reliable, high-performance bill acceptor that has means to absorb and discharge static electricity, eliminating interferences of electromagnetic noises.